A new drug called Arimidex has been found to be more effective than tamoxifen at preventing the return of breast cancer in women who have had the disease. CNN reports, "The drug, Arimidex, might be able to prevent 70 percent to 80 percent of the most common type of tumors that occur in women after menopause, compared with the 50 percent that tamoxifen is credited with warding off, their research suggests." AstraZeneca PLC, the manufacturer of Arimidex, reported these results on Wednesday and its study may be found on-line at the British medical journal, The Lancet.